In magnetic resonance imaging, motion of directional fluid is depicted, for example, by phase contrast method or diffusion weighted imaging. Movement of protons that is restricted to a specific orientation because of the myelin sheath in the axon, for example, can be depicted using diffusion weighted imaging, with an application of a pulse of a high b-value, such as to the extent of b=1000 to 2000 sec/mm2.
However, as for the production/absorption of CSF (Cerebrospinal Fluid) or proton movement from arteries to veins in the capillary bed, depiction was difficult by these methods.